Summary
The objective of this procedure is to show you how to check ignition timing using a timing light. It is not necessary for the technician to alter the timing from the manufacturer's specifications. In some cases, serious damage could result.
Part 1. Preparation and safety
Objective
- Check ignition timing using a timing light.
Personal safety
Whenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies. Among other items, this may include:
- Work clothing - such as coveralls and steel-capped footwear
- Eye protection - such as safety glasses and face masks
- Ear protection - such as earmuffs and earplugs
- Hand protection - such as rubber gloves and barrier cream
- Respiratory equipment - such as face masks and valved respirators
If you are not certain what is appropriate or required, ask your supervisor.
Safety check
- This method of checking the timing can only be performed with the engine running so the belts and fans are moving. As you point the timing light onto the engine timing marks, be careful not to reach into the engine compartment far enough to be injured by any of the moving components.
- Remember, the light makes the engine rotating parts look as if they are standing still, but they are still moving and dangerous!
- Make sure that the hood is secure with the hood stay rod.
- Always make sure that you wear the appropriate personal protection equipment before starting the job. It is very easy to hurt yourself even when the most exhaustive protection measures are taken.
- Always make sure that your work area/environment is as safe as you can make it. Do not use damaged, broken or worn out workshop equipment.
- Always follow any manufacturer's personal safety instructions to prevent damage to the vehicle you are working on.
- Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks. If you are unsure of what these are, ask your supervisor.
Points to note
- The timing light is a strobe light that is fired for a fraction of a second whenever the first spark plug fires inside the cylinder. When the light is pointed at the timing marks, the rapid sequence of flashes appears to freeze the engine in the same place on every stroke of the cylinder and consequent rotation of the crankshaft. This allows you to see clearly a special timing mark on the crankshaft pulley (or harmonic balancer), and where it is in relation to another mark on the engine. This will tell you whether the spark is firing at the correct time, or ahead or behind when it is supposed to fire. "Ahead" means the timing is "advanced" and "behind" means the timing is "retarded". In normal operation, advancing and retarding the ignition timing from the set point is desirable. However, this is controlled by the ignition system. It is not necessary for the technician to alter the timing from the manufacturer's specifications. In some cases, serious damage could result.
- Different manufacturers number their cylinders from different ends of the engine, so check the workshop manual if you are not sure which is the number one cylinder.
Part 2: Step-by-step instruction
- Locate crankshaft and spark plug
Locate the position of the timing marks. These are normally on the front of the engine on the crankshaft pulley or harmonic balancer, with a corresponding mark on the engine block. Locate the number one cylinder spark plug. If you are not sure which is the number one cylinder, refer to the workshop manual.
- Connect timing light
Attach the timing light cable on to the High Tension Lead leading to the number one cylinder. Then connect the power leads to the battery – red lead to the positive terminal, black to the negative terminal.
- Check position of the timing mark
Start the engine and point the timing light at the timing marks. Be careful not to touch any of the moving or hot components in the engine compartment. Note where the timing mark on the rotating crankshaft appears to be in relation to the stationary reference mark at engine idle speed. Compare this with the specification in the workshop manual. Rev the engine briefly to about 2500rpm. And note the position of the timing mark again. The timing should have advanced. If it does not, this could indicate a problem. Switch off the engine and detach the light cable. Report to your supervisor any reading, which is outside the specification.
